Water for heating and cooling apparatus must be purified or treated to avoid a plurality of problems. More specifically, boilers and cooling towers require pure water for optimal performance. However, the water coming into these systems is generally impure and contains contaminants which can foul the boiler and cooling tower.
Feed water is generally contaminated with gases, such as oxygen and carbon dioxide. In addition, water can leach impurities from the air. These impurities lead to scale formation, corrosion, and pitting. A major contaminant in many water systems is iron, often leached from water lines.
In cooling towers, such problems may escalate due to evaporation of the water, thereby increasing concentration of the contaminants and resulting in a higher rate of subsequent corrosion and deposition tendencies. Higher temperatures also tends to increase corrosion potential. A longer retention time of contaminants in the water coupled with warmer water tends to reduce the effectiveness of heat transfer surfaces and increases the potential for microbiological growth.
Currently there are a variety of different physical and chemical treatments for contaminated water. Conventional treatments for water systems, such as a boiler, have included the use of amines, particularly to scavenge oxygen and neutralize carbon dioxide. These amines are generally volatile having boiling points comparable to the elevated temperatures achieved in the boiler and generally vaporize into the steam to treat the resulting condensate. However, amines, commonly used to treat water, are typically commercially available only as liquids. Conventional water treatment compositions containing such amines are generally prepared and stored as liquids. These liquid compositions typically emit repugnant and potentially toxic odors which may be detected during manufacture, packaging, or shipping processes, and particularly during the use in treating boiler water.
Corrosion inhibiting chemicals as disclosed in U.S. Pat. No. 4,066,398 have been used to treat contaminated water. U.S. Pat. No. 3,510,436 discloses the use of organic phosphates or phosphonates in combination with zinc and/or mercaptobenzothiazole for corrosion inhibition in water systems including cooling towers. Compositions utilizing chromates and inorganic polyphosphates have been used to inhibit corrosion of metal surfaces in contact with cooling tower water. However, such treatments are undesirable, both from the viewpoint of handling personnel health and also problems associated with waste disposal. Phosphates are generally non-toxic. However, due to hydrolysis of polyphosphates to orthophosphates and the limited solubility of calcium orthophosphate, which is likely to form, it has been impossible in many instances to maintain adequate concentrations of phosphates. Furthermore, from a water pollution standpoint, effluent containing a sufficiently high phosphate residual, may serve as a nutrient to aquatic life. For these reasons, the use of chromates, inorganic phosphates and other phosphates have been entirely unsatisfactory.
Thus, there remains a need to provide a composition to treat water in water flow systems effectively and safely, from a health and handling perspective, with minimal waste disposal problems.